U.S. patent application number 14/630386 was filed with the patent office on 2016-04-21 for estimation of spur parameters in wireless communications.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Hassan Rafique.
Application Number | 20160112976 14/630386 |
Document ID | / |
Family ID | 54337399 |
Filed Date | 2016-04-21 |
United States Patent
Application |
20160112976 |
Kind Code |
A1 |
Rafique; Hassan |
April 21, 2016 |
ESTIMATION OF SPUR PARAMETERS IN WIRELESS COMMUNICATIONS
Abstract
Aspects of the present disclosure provide for an apparatus
configured to receive a communication signal including a spur
utilizing a communication interface. The apparatus determines a
first estimated frequency of the spur and a first estimated
duration of the spur based on the first estimated frequency
utilizing a searching algorithm. The apparatus determines a second
estimated frequency of the spur based on the first estimated
duration utilizing the searching algorithm, and a second estimated
duration of the spur based on the second estimated frequency
utilizing the searching algorithm. The apparatus determines at
least one of an amplitude, a start location, or a phase offset of
the spur based on the second estimated frequency and the second
estimated duration.
Inventors: |
Rafique; Hassan;
(Farnborough, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
54337399 |
Appl. No.: |
14/630386 |
Filed: |
February 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62064123 |
Oct 15, 2014 |
|
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62064113 |
Oct 15, 2014 |
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Current U.S.
Class: |
370/330 |
Current CPC
Class: |
H04J 11/0066 20130101;
H04L 5/0062 20130101; H04W 56/003 20130101; H04B 1/1036 20130101;
H04W 72/1231 20130101; H04L 5/0005 20130101 |
International
Class: |
H04W 56/00 20060101
H04W056/00; H04L 5/00 20060101 H04L005/00; H04W 72/12 20060101
H04W072/12 |
Claims
1. A method of determining spur parameters in a communication
signal, comprising: receiving a communication signal comprising a
spur utilizing a communication interface; determining a first
estimated frequency of the spur; determining a first estimated
duration of the spur based on the first estimated frequency
utilizing a searching algorithm; determining a second estimated
frequency of the spur based on the first estimated duration
utilizing the searching algorithm; determining a second estimated
duration of the spur based on the second estimated frequency
utilizing the searching algorithm; and determining at least one of
an amplitude, a start location, or a phase offset of the spur based
on the second estimated frequency and the second estimated
duration.
2. The method of claim 1, wherein the searching algorithm comprises
a cost function with a frequency variable and a duration
variable.
3. The method of claim 2, wherein the determining the first
estimated duration comprises determining a minimum value of the
cost function while setting the frequency variable equal to the
first estimated frequency of the spur.
4. The method of claim 2, wherein the determining the second
estimated frequency of the spur comprises determining a minimum
value of the cost function while setting the duration variable
equal to the first estimated duration.
5. The method of claim 2, wherein the determining the second
estimated duration comprises determining a minimum value of the
cost function while setting the frequency variable equal to the
second estimated frequency of the spur.
6. The method of claim 1, wherein the first estimated frequency of
the spur is less accurate than the second estimated frequency of
the spur.
7. The method of claim 1, wherein the first estimated duration of
the spur is less accurate than the second estimated duration of the
spur.
8. The method of claim 1, wherein fast Fourier transform (FFT)
samples of the communication signal comprise a maximum FFT sample
k.sub.max, a first adjacent FFT sample k.sub.max-1, and a second
adjacent FFT sample k.sub.max+1; and wherein the determining the
first estimated frequency of the spur comprises determining the
first estimated frequency as a weighted average of a first angle
based on the maximum FFT sample k.sub.max and the first adjacent
FFT sample k.sub.max-1, and a second angle based on the maximum FFT
sample k.sub.max and the second adjacent FFT sample
k.sub.max+1.
9. An apparatus comprising: means for receiving a communication
signal comprising a spur; means for determining a first estimated
frequency of the spur; means for determining a first estimated
duration of the spur based on the first estimated frequency
utilizing a searching algorithm; means for determining a second
estimated frequency of the spur based on the first estimated
duration utilizing the searching algorithm; means for determining a
second estimated duration of the spur based on the second estimated
frequency utilizing the searching algorithm; and means for
determining at least one of an amplitude, a start location, or a
phase offset of the spur based on the second estimated frequency
and the second estimated duration.
10. The apparatus of claim 9, wherein the searching algorithm
comprises a cost function with a frequency variable and a duration
variable.
11. The apparatus of claim 10, wherein the means for determining
the first estimated duration is configured to determine a minimum
value of the cost function while setting the frequency variable
equal to the first estimated frequency of the spur.
12. The apparatus of claim 10, wherein the means for determining
the second estimated frequency of the spur is configured to
determine a minimum value of the cost function while setting the
duration variable equal to the first estimated duration.
13. The apparatus of claim 10, wherein the means for determining
the second estimated duration is configured to determine a minimum
value of the cost function while setting the frequency variable
equal to the second estimated frequency of the spur.
14. The apparatus of claim 9, wherein the first estimated frequency
of the spur is less accurate than the second estimated frequency of
the spur.
15. The apparatus of claim 9, wherein the first estimated duration
of the spur is less accurate than the second estimated duration of
the spur.
16. The apparatus of claim 9, wherein fast Fourier transform (FFT)
samples of the communication signal comprises a maximum FFT sample
k.sub.max, a first adjacent FFT sample k.sub.max-1, and a second
adjacent FFT sample k.sub.max+1, and wherein the means for
determining the first estimated frequency of the spur is configured
to determine the first estimated frequency as a weighted average of
a first angle based on the maximum FFT sample k.sub.max and the
first adjacent FFT sample k.sub.max-1, and a second angle based on
the maximum FFT sample k.sub.max and the second adjacent FFT sample
k.sub.max+1.
17. An apparatus comprising: a communication interface; a
computer-readable medium comprising a spur parameters estimation
code; and at least one processor coupled to the communication
interface and the computer-readable medium, wherein the at least
one processor when executing the spur parameters estimation code,
is configured to: receive a communication signal comprising a spur
utilizing the communication interface; determine a first estimated
frequency of the spur; determine a first estimated duration of the
spur based on the first estimated frequency utilizing a searching
algorithm; determine a second estimated frequency of the spur based
on the first estimated duration utilizing the searching algorithm;
determine a second estimated duration of the spur based on the
second estimated frequency utilizing the searching algorithm; and
determine at least one of an amplitude, a start location, or a
phase offset of the spur based on the second estimated frequency
and the second estimated duration.
18. The apparatus of claim 17, wherein the searching algorithm
comprises a cost function with a frequency variable and a duration
variable.
19. The apparatus of claim 18, wherein the at least one processor
when executing the spur parameters estimation code, is further
configured to: minimize the cost function while setting the
frequency variable equal to the first estimated frequency of the
spur.
20. The apparatus of claim 18, wherein the at least one processor
when executing the spur parameters estimation code, is further
configured to: minimize the cost function while setting the
duration variable equal to the first estimated duration of the
spur.
21. The apparatus of claim 18, wherein the at least one processor
when executing the spur parameters estimation code, is further
configured to: minimize the cost function while setting the
frequency variable equal to the second estimated frequency of the
spur.
22. The apparatus of claim 17, wherein the first estimated
frequency of the spur is less accurate than the second estimated
frequency of the spur.
23. The apparatus of claim 17, wherein the first estimated duration
of the spur is less accurate than the second estimated duration of
the spur.
24. The apparatus of claim 17, wherein fast Fourier transform (FFT)
samples of the communication signal comprises a maximum FFT sample
k.sub.max, a first adjacent FFT sample k.sub.max-1, and a second
adjacent FFT sample k.sub.max+1, and wherein the at least one
processor when executing the spur parameters estimation code, is
further configured to determine the first estimated frequency as a
weighted average of a first angle based on the maximum FFT sample
k.sub.max and the first adjacent FFT sample k.sub.max-1, and a
second angle based on the maximum FFT sample k.sub.max and the
second adjacent FFT sample k.sub.max+1.
25. A computer-readable medium comprising code for causing an
apparatus to determine spur parameters in a communication signal,
the code causing the apparatus to: receive a communication signal
comprising a spur utilizing a communication interface; determine a
first estimated frequency of the spur; determine a first estimated
duration of the spur based on the first estimated frequency
utilizing a searching algorithm; determine a second estimated
frequency of the spur based on the first estimated duration
utilizing the searching algorithm; determine a second estimated
duration of the spur based on the second estimated frequency
utilizing the searching algorithm; and determine at least one of an
amplitude, a start location, or a phase offset of the spur based on
the second estimated frequency and the second estimated
duration.
26. The computer-readable medium of claim 25, wherein the searching
algorithm comprises a cost function with a frequency variable and a
duration variable.
27. The computer-readable medium of claim 26, wherein for
determining the first estimated duration, the code further causes
the apparatus to determine a minimum value of the cost function
while setting the frequency variable equal to the first estimated
frequency of the spur.
28. The computer-readable medium of claim 26, wherein for
determining the second estimated frequency of the spur, the code
further causes the apparatus to determine a minimum value of the
cost function while setting the duration variable equal to the
first estimated duration.
29. The computer-readable medium of claim 26, wherein for
determining the second estimated duration, the code further causes
the apparatus to determine a minimum value of the cost function
while setting the frequency variable equal to the second estimated
frequency of the spur.
30. The computer-readable medium of claim 25, wherein fast Fourier
transform (FFT) samples of the communication signal comprise a
maximum FFT sample k.sub.max, a first adjacent FFT sample
k.sub.max-1, and a second adjacent FFT sample k.sub.max+1; and
wherein for determining the first estimated frequency of the spur,
the code further causes the apparatus to determine the first
estimated frequency as a weighted average of a first angle based on
the maximum FFT sample k.sub.max and the first adjacent FFT sample
k.sub.max-1, and a second angle based on the maximum FFT sample
k.sub.max and the second adjacent FFT sample k.sub.max+1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
provisional patent application nos. 62/064,123 and 62/064,113 both
filed in the United States Patent and Trademark Office on 15 Oct.
2014, the entire contents of these applications are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The technology discussed below relates generally to wireless
communication systems, and more particularly, to detection and
estimation of spurs or tones.
BACKGROUND
[0003] Wireless communication networks are widely deployed to
provide various communication services such as telephony, video,
data, messaging, broadcasts, and so on. Such networks, which are
usually multiple access networks, support communications for
multiple users by sharing the available network resources. One
example of such a network is the UMTS Terrestrial Radio Access
Network (UTRAN). The UTRAN is the radio access network (RAN)
defined as a part of the Universal Mobile Telecommunications System
(UMTS), a third generation (3G) mobile phone technology supported
by the 3rd Generation Partnership Project (3GPP). UMTS, which is
the successor to Global System for Mobile Communications (GSM)
technologies, currently supports various air interface standards,
such as Wideband-Code Division Multiple Access (W-CDMA), Time
Division-Code Division Multiple Access (TD-CDMA), and Time
Division-Synchronous Code Division Multiple Access (TD-SCDMA). UMTS
also supports enhanced 3G data communications protocols, such as
High Speed Packet Access (HSPA), which provides higher data
transfer speeds and capacity to associated UMTS networks.
[0004] Spurs or spurious signals are narrowband noise that can
undesirably affect the communication between wireless communication
devices such as base stations and mobile terminals. At a mobile
terminal, spurs can emanate from the oscillator and related
circuitry used for clocking and tuning purposes. They can be
realized as complex tones that can interfere with the desired
signal, directly or indirectly. In the context of adjacent-channel
interference (ACI) detection, spurs may cause false alarms and
invoke signal processing algorithms that are not suitable for that
scenario, which can compromise ACI performance. Furthermore, during
channel acquisition, spurs may get detected as potential frequency
correction channel tones coming from a base station and can delay
the acquisition process due to unnecessary synchronization channel
scheduling.
SUMMARY
[0005] The following presents a simplified summary of one or more
aspects of the present disclosure, in order to provide a basic
understanding of such aspects. This summary is not an extensive
overview of all contemplated features of the disclosure, and is
intended neither to identify key or critical elements of all
aspects of the disclosure nor to delineate the scope of any or all
aspects of the disclosure. Its sole purpose is to present some
concepts of one or more aspects of the disclosure in a simplified
form as a prelude to the more detailed description that is
presented later.
[0006] In one aspect, the disclosure provides a method of
determining spur parameters in a communication signal operable by
an apparatus. The apparatus receives a communication signal
including a spur utilizing a communication interface. The apparatus
determines a first estimated frequency of the spur. The apparatus
determines a first estimated duration of the spur based on the
first estimated frequency utilizing a searching algorithm. The
apparatus determines a second estimated frequency of the spur based
on the first estimated duration utilizing the searching algorithm.
The apparatus determines a second estimated duration of the spur
based on the second estimated frequency utilizing the searching
algorithm. The apparatus determines at least one of an amplitude, a
start location, or a phase offset of the spur based on the second
estimated frequency and the second estimated duration.
[0007] Another aspect of the disclosure provides an apparatus
configured to determine spur parameters in a communication signal.
The apparatus includes means for receiving a communication signal
including a spur. The apparatus further includes means for
determining a first estimated frequency of the spur, and means for
determining a first estimated duration of the spur based on the
first estimated frequency utilizing a searching algorithm. The
apparatus further includes means for determining a second estimated
frequency of the spur based on the first estimated duration
utilizing the searching algorithm, and means for determining a
second estimated duration of the spur based on the second estimated
frequency utilizing the searching algorithm. The apparatus further
includes means for determining at least one of an amplitude, a
start location, or a phase offset of the spur based on the second
estimated frequency and the second estimated duration.
[0008] Another aspect of the disclosure provides an apparatus
configured to determine spur parameters in a communication signal.
The apparatus includes a communication interface, a
computer-readable medium including a spur parameters estimation
code, and at least one processor coupled to the communication
interface and the computer-readable medium. The at least one
processor when executing the spur parameters estimation code, is
configured to receive a communication signal including a spur
utilizing the communication interface. The at least one processor
is further configured to determine a first estimated frequency of
the spur, and a first estimated duration of the spur based on the
first estimated frequency utilizing a searching algorithm. The at
least one processor is further configured to determine a second
estimated frequency of the spur based on the first estimated
duration utilizing the searching algorithm, and a second estimated
duration of the spur based on the second estimated frequency
utilizing the searching algorithm. The at least one processor is
further configured to determine at least one of an amplitude, a
start location, or a phase offset of the spur based on the second
estimated frequency and the second estimated duration.
[0009] Another aspect of the disclosure provides a
computer-readable medium including code for causing an apparatus to
determine spur parameters in a communication signal. The code
causes the apparatus to receive a communication signal including a
spur utilizing a communication interface. The code further causes
the apparatus to determine a first estimated frequency of the spur,
and a first estimated duration of the spur based on the first
estimated frequency utilizing a searching algorithm. The code
further causes the apparatus to determine a second estimated
frequency of the spur based on the first estimated duration
utilizing the searching algorithm, and a second estimated duration
of the spur based on the second estimated frequency utilizing the
searching algorithm. The code further causes the apparatus to
determine at least one of an amplitude, a start location, or a
phase offset of the spur based on the second estimated frequency
and the second estimated duration.
[0010] These and other aspects of the invention will become more
fully understood upon a review of the detailed description, which
follows. Other aspects, features, and embodiments of the present
invention will become apparent to those of ordinary skill in the
art, upon reviewing the following description of specific,
exemplary embodiments of the present invention in conjunction with
the accompanying figures. While features of the present invention
may be discussed relative to certain embodiments and figures below,
all embodiments of the present invention can include one or more of
the advantageous features discussed herein. In other words, while
one or more embodiments may be discussed as having certain
advantageous features, one or more of such features may also be
used in accordance with the various embodiments of the invention
discussed herein. In similar fashion, while exemplary embodiments
may be discussed below as device, system, or method embodiments it
should be understood that such exemplary embodiments can be
implemented in various devices, systems, and methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram illustrating an example of an apparatus
operable to detect spurs and estimate spur parameters in accordance
with aspects of the disclosure.
[0012] FIG. 2 is a drawing illustrating spur classifications and
impact according to some aspects of the disclosure.
[0013] FIG. 3 shows two graphs illustrating the fast Fourier
transform (FFT) of a spur and a non-spurious signal spur according
to some aspects of the disclosure.
[0014] FIG. 4 is another graph illustrating the spur of FIG. 3
standing out from the non-spurious signal when both signals are
shown in the same graph.
[0015] FIG. 5 is a graph illustrating the FFT of a 200 kHz spur and
a 200.5 kHz spur according to some aspects of the disclosure.
[0016] FIG. 6 is a graph illustrating the FFT of a 200.4 kHz spur
sampled at a frequency of 270.833.times.4 kHz.
[0017] FIG. 7 is a flow chart illustrating a spur parameters
determination method in accordance with some aspects of the
disclosure.
[0018] FIG. 8 is a graph illustrating examples of estimated rough
values of a spur duration according to a cost function.
[0019] FIG. 9 is a flow chart illustrating a rough spur duration
determination method in accordance with some aspects of the
disclosure.
[0020] FIG. 10 is a flow chart illustrating a fine spur frequency
determination method in accordance with some aspects of the
disclosure.
[0021] FIG. 11 is a flow chart illustrating a fine spur duration
determination method in accordance with some aspects of the
disclosure.
DETAILED DESCRIPTION
[0022] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
configurations and is not intended to represent the only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of various
concepts. However, it will be apparent to those skilled in the art
that these concepts may be practiced without these specific
details. In some instances, well known structures and components
are shown in block diagram form in order to avoid obscuring such
concepts.
[0023] FIG. 1 is a diagram illustrating an example of an apparatus
100 operable to detect spurs and estimate spur parameters in
accordance with aspects of the disclosure. In accordance with
various aspects of the disclosure, an element, or any portion of an
element, or any combination of elements may be implemented with a
processing system 114 that includes one or more processors 104. For
example, the apparatus 100 may be a user equipment (UE). In another
example, the apparatus 100 may be a radio network controller (RNC)
or a base station. Examples of processors 104 include
microprocessors, microcontrollers, digital signal processors
(DSPs), field programmable gate arrays (FPGAs), programmable logic
devices (PLDs), state machines, gated logic, discrete hardware
circuits, and other suitable hardware configured to perform the
various functionality described throughout this disclosure. For
example, the processor 104, as utilized in an apparatus 100, may be
used to implement any one or more of the processes and functions
described below and illustrated in FIGS. 2-11. In various aspects
of the disclosure, the components, modules, circuitry, and/or
blocks of the apparatus 100, shown or not shown in FIG. 1, may be
implemented in software, hardware, firmware, or a combination
thereof.
[0024] In this example, the processing system 114 may be
implemented with a bus architecture utilizing a bus. The bus may
include any number of interconnecting buses and bridges depending
on the specific application of the processing system 114 and the
overall design constraints. The bus links together various circuits
including one or more processors (represented generally by the
processor 104), a memory 105, and computer-readable media
(represented generally by the computer-readable medium 106). The
bus may also link various other circuits such as timing sources,
peripherals, voltage regulators, and power management circuits,
which are well known in the art, and therefore, will not be
described any further. A bus interface provides an interface
between the bus and a communication interface 110 including, for
example, a transceiver 111 and other known circuitry in the art for
wireless communications. The communication interface 110 provides a
means for communicating (e.g., transmitting and receiving wireless
signals) with various other apparatus over a transmission medium.
Depending upon the nature of the apparatus, a user interface 112
(e.g., keypad, display, speaker, microphone, joystick, touchscreen,
touchpad, gesture sensor) may also be provided.
[0025] The processor 104 includes a spur parameters estimation
block 120 that can be configured to perform various functions to
estimate the parameters of a spur or spurious signal in a
communication signal, which may be received via the communication
interface 110. In one aspect of the disclosure, the spur parameters
estimation block 120 includes a rough spur duration estimation
block 122, a fine spur duration estimation block 124, a fine spur
frequency estimation block 126, and a rough spur frequency
estimation block 128. The spur parameters estimation block 120
further includes an ASP estimation block 130 for determining spur
amplitude, start position, and phase offset. The rough spur
duration estimation block 122 may be configured to determine a
rough estimate of the spur duration using a searching algorithm
132. The fine spur duration estimation block 124 may be configured
to determine a fine estimate of the spur duration using a searching
algorithm. The fine spur frequency estimation block 126 may be
configured to determine a fine estimate of the spur frequency using
a searching algorithm. The rough spur frequency estimation block
128 may be configured to determine a rough estimate of the spur
frequency. The searching algorithm 132 may be stored in the
computer-readable medium 106 or the processor 104. The various
blocks (122, 124, 126, and 128) of the spur parameters estimation
block 120 may utilize the same or different searching
algorithm.
[0026] The processor 104 also includes a fast Fourier transform
(FFT) block 134 that can be configured to perform FFT operations on
signal samples to generate frequency domain data. A spur detection
block 136 may be configured to detect the presence of spurs in a
communication signal. The above components or blocks will be
described in more detail below in some illustrative examples.
[0027] The computer-readable medium 106 may include a spur
parameters estimation routine 138 that when executed by the
processor 104, can configure the spur parameters estimation block
120, FFT block 134, and spur detection block 136 to perform various
functions, for example, to detect, estimate and/or determine the
parameters of a spur or a tone. In some aspects of the disclosure,
the spur parameters estimation block 120 may be configured to
estimate or determine the frequency, amplitude, duration, start
time, and/or phase offset of a spur or a tone. The
computer-readable medium 106 may include an FFT routine 140 when
executed by the processor 104, can configure the FFT block 134 to
perform various FFT functions on signal data.
[0028] The processor 104 is also responsible for managing the bus
and general processing, including the execution of software stored
on the computer-readable medium 106. The software, when executed by
the processor 104, causes the processing system 114 to perform the
various functions described below for any particular apparatus. The
computer-readable medium 106 may also be used for storing data that
is manipulated by the processor 104 when executing software. For
example, the computer-readable medium 106 may be used to store
signal samples of a communication signal received by the apparatus,
and other data generated or utilized by the processor 104.
[0029] One or more processors 104 in the processing system may
execute various software. Software shall be construed broadly to
mean instructions, instruction sets, code, code segments, program
code, programs, subprograms, software modules, applications,
software applications, software packages, routines, subroutines,
objects, executables, threads of execution, procedures, functions,
etc., whether referred to as software, firmware, middleware,
microcode, hardware description language, or otherwise. The
software may reside on a computer-readable medium 106. The
computer-readable medium 106 may be a non-transitory
computer-readable medium. A non-transitory computer-readable medium
includes, by way of example, a magnetic storage device (e.g., hard
disk, floppy disk, magnetic strip), an optical disk (e.g., a
compact disc (CD) or a digital versatile disc (DVD)), a smart card,
a flash memory device (e.g., a card, a stick, or a key drive), a
random access memory (RAM), a read only memory (ROM), a
programmable ROM (PROM), an erasable PROM (EPROM), an electrically
erasable PROM (EEPROM), a register, a removable disk, and any other
suitable medium for storing software and/or instructions that may
be accessed and read by a computer. The computer-readable medium
106 may reside in the processing system 114, external to the
processing system 114, or distributed across multiple entities
including the processing system 114. The computer-readable medium
106 may be embodied in a computer program product. By way of
example, a computer program product may include a computer-readable
medium in packaging materials. Those skilled in the art will
recognize how best to implement the described functionality
presented throughout this disclosure depending on the particular
application and the overall design constraints imposed on the
overall system.
[0030] FIG. 2 is a drawing illustrating examples of spur
classifications and impact in accordance with aspects of the
disclosure. In a first scenario 202, if a spur or spurious signal
is located at or near a carrier of a desired absolute
radio-frequency channel number (ARFCN), the spur may directly
impact such carrier and its acquisition. In a second scenario 204,
if a spur is located at or near the carriers of adjacent ARFCNs,
the spur may still indirectly impact the desired ARFCN and its
acquisition.
[0031] Aspects of the disclosure provide a method that can detect a
spur and estimate the spur (or tone) parameters given that the
existence of the spur is known. Non-limiting examples of the spur
parameters are frequency, amplitude, duration, start time, and
phase offset. The existence of spurs may be determined by using any
suitable methods or processes. In one example, a method for
determining the existence of spurs is disclosed in a co-pending
patent application, titled Adjacent-Channel Interference and Spur
Handling in Wireless Communications (Attorney Docket No. 146416,
application Ser. No. ______), filed on even date herewith in the
United States Patent and Trademark Office, which is incorporated
herein in its entirety by reference.
[0032] A spur is monotonic in nature and have its energies
concentrated around its frequency. FIG. 3 are two graphs
illustrating the magnitude responses of a spur 302 and a
non-spurious signal 304 in accordance with an aspect of the
disclosure. The energy gradient of the spur 302 against frequency
is quite steep relative to that of the non-spurious signal 304.
When compared to the non-spurious signal 304 (e.g., a GSM carrier),
it can be seen that the spur 302 has a substantially more prominent
peak 306, which can be considered an outlier among the data set.
FIG. 4 is another graph illustrating the spur 302 standing out from
the non-spurious signal 304 when both signals are shown in the same
graph.
[0033] In one aspect of the disclosure, the spur 302 or a spurious
signal can be detected by utilizing a peak to average ratio (PAR)
computed in the frequency domain as defined by equation (1) below.
The spur detection block 136 may be utilized to perform the below
described processes to detect a spur based on PAR.
[0034] Let the FFT of the signal x[n] samples be X[k] as shown in
equation (0). FFT or discrete Fourier transform (DFT) may be used
interchangeably in this specification.
X [ k ] = n = 0 N - 1 x [ n ] - j 2 .pi. k N n ( 0 ) k : 0 , 1 , N
##EQU00001##
[0035] In equation (0), X[k] is the frequency domain data of the
signal x[n]. Then, the PAR can be computed as follows:
PAR = max ( X [ k ] ) 1 k 2 - k 1 + 1 k = k 1 k 2 X [ k ] .
##EQU00002##
[0036] N is the FFT windows size, k1 is the FFT bin start, and k2
is the FFT bin end. A bin is a spectrum sample, and defines the
frequency resolution of the FFT window. When the PAR is greater
than a spur detection threshold (e.g., a predetermined threshold),
it indicates that spur is detected. In one example, the spur
detection threshold may be set to about 10 dB or any suitable
value.
[0037] A spur can be represented in the time domain as equation
(1).
x [ n ] = A j ( 2 .pi. F spur F s n + .PHI. ) n : a , a + 1 , a + 2
, a + N _ - 1 ( 1 ) ##EQU00003##
[0038] In equation (1), a is the start of the spur in unit of time
(e.g., an offset from a measurement period where the spur starts, N
is the duration, F.sub.spur is the spur frequency, F.sub.s is the
sampling frequency, N is the fast Fourier transform (FFT) window
size, and .phi. is the initial phase offset. Taking the FFT of the
time domain equation (1), produces the following equations.
X [ k ] = n = 0 N - 1 x [ n ] - j2.pi. k N n k : 0 , 1 , N ( 2 ) X
[ k ] = n = a a + N _ - 1 A j ( 2 .pi. F spur F s n + .PHI. ) - j 2
.pi. k N n X [ k ] = n = a a + N _ - 1 A j [ 2 .pi. n ( F spur F s
k N ) + .PHI. ] , let .alpha. = F spur F s - k N X [ k ] = n = a a
+ N _ - 1 A j [ 2 .pi. n .alpha. + .PHI. ] x [ k ] = A j.PHI. [ j 2
.pi..alpha..alpha. + j 2 .pi. ( .alpha. + 1 ) .alpha. + j 2 .pi. (
.alpha. + 2 ) .alpha. + j2.pi. ( .alpha. + N _ - 1 ) .alpha. ]
##EQU00004##
Taking e.sup.j2.pi..alpha..alpha. as a common term, X[k] can be
simplified.
X [ k } = A j .PHI. j 2 .pi..alpha..alpha. [ 1 + j 2 .pi. .alpha. +
j 4 .pi..alpha. + j 2 .pi. ( N _ - 1 ) .alpha. ] X [ k ] = A j
.PHI. j 2 .pi..alpha..alpha. 1 - j 2 .pi..alpha. N _ 1 - j 2
.pi..alpha. X [ k ] = A j .PHI. j 2 .pi. .alpha..alpha. j
.pi..alpha. N _ - j.pi..alpha. N _ - j.pi..alpha. N _ j .pi..alpha.
( - j.pi..alpha. - j .pi. .alpha. ) X [ k ] = A j [ .pi. .alpha. (
N _ + 1 + 2 .alpha. ) + .PHI. ] sin ( .pi..alpha. N _ ) sin ( .pi.
.alpha. ) ( 2.1 ) X [ k ] = A sin ( .pi. .alpha. N _ ) sin ( .pi.
.alpha. ) ( 3 ) .theta. [ k ] = .pi. .alpha. ( N _ - 1 + 2 .alpha.
) + .PHI. ( 4 ) ##EQU00005##
Where |X[k]| is the magnitude, and .theta.[k] is the phase. Now,
substitute
.alpha. = F spur F s - k N ##EQU00006##
in equation (4) and rearrange the terms of the equation to get
equation (5).
.theta. [ k ] = - k .pi. ( N _ - 1 + 2 .alpha. ) N + F spur .pi. (
N _ - 1 + 2 .alpha. ) F s + .PHI. .theta. [ k ] = - km + C , where
, ( 5 ) m = .pi. ( N _ - 1 + 2 .alpha. ) N ( 6 ) C = F spur .pi. (
N _ - 1 + 2 .alpha. ) F s + .PHI. ( 7 ) ##EQU00007##
[0039] From the above equations (2) through (7), the five unknown
spur parameters are A, F.sub.spur, N, a, and .phi.. Therefore, the
spur can be estimated by determining these five spur parameters.
According to aspects of the disclosure, these five unknown
parameters can be solved by using a searching algorithm for
determining the values of F.sub.spur and N, followed by solving the
remaining unknowns using equations (4) and (6). The searching
algorithm may be any suitable algorithm that can be utilized to
find the values of F.sub.spur and N. In one aspect of the
disclosure, using the values of k.sub.max and k.sub.max+1 of the
spur spectrum, the searching algorithm may be implemented as a cost
function (8) shown below.
C ( k , F spur , N _ ) = arg min { F spur , N _ } X [ k max + 1 ] X
[ k max ] - R [ k max + 1 ] R [ k max ] ( 8 ) ##EQU00008##
[0040] In this example, the searching algorithm includes the
operations utilized for finding the values of F.sub.spur and N that
can minimize the cost function (8). Either one of the values of
F.sub.spur and N may be set to a predetermined value, and the value
of the cost function (8) may be determined. This process may be
performed iteratively until a desired value (e.g., a minimum value)
of the cost function (8) is achieved, for example, as illustrated
in FIG. 7 below.
[0041] In equation (8), R[k] is the FFT of the received signal
data, X[k] is the theoretical expression of equation (3) with A=1.
The use of ratios in equation (8) eliminates A from the equations,
and the search variables become F.sub.spur (frequency variable) and
N (duration variable). The value k.sub.max is the FFT sample with
the maximum spectrum value.
[0042] The search region for duration N is 1: N.sub.total, where,
N.sub.total is the number of samples used in the FFT. The search
region for F.sub.spur is [F1 to F2] that is defined according to
the following rule:
F 1 = F S * k max N , F 2 = R [ k max + 1 ] > R [ k max - 1 ] ?
F S * k max + 1 N : F S * k max - 1 N . ##EQU00009##
[0043] F1 is the frequency where the peak occurs, and F2 is the
equivalent frequency of the sample on the left or right depending
on the relationship above.
[0044] FIG. 5 is a graph illustrating the FFT of exemplary 200 kHz
spur and 200.5 kHz spur sampled at 270.83.times.4 kHz (sampling
frequency). Depending on the sampling frequency, the FFT may or may
not sample the peak of the spurs. In the examples shown in FIG. 5,
the 200 kHz spur 502 is sampled close to its peak, while the 200.5
kHz spur 504 is not. Therefore, in one aspect of the disclosure,
the search region may be defined to be between the frequencies
where the maximum sample and second highest sample lie. As
illustrated in FIG. 5, if the peak of a spur (e.g., spur 502) gets
sampled, the values to the left and right of the peak will be
similar in magnitude. In one example, when the FFT is performed at
F.sub.s=270.833.times.4 (sampling frequency) and N=1024, the
frequency resolution of the FFT is about 1.05 kHz. Therefore, the
estimation error is about +/-500 Hz, if the sampled peak is taken
as the spur frequency.
[0045] FIG. 6 is a graph illustrating the FFT of a 200.4 kHz spur
sampled at a frequency of 270.833.times.4 kHz. However, in FIG. 6,
the peak of the FFT is at about 200 kHz (k.sub.max), which is not
the actual peak of the spur (200.4 kHz). In FIG. 6, the angle
.theta..sub.1 corresponds to an angle formed by the max FFT sample
k.sub.max and the adjacent FFT sample k.sub.max-1, and the angle
.theta..sub.2 corresponds to an angle formed by the max FFT sample
k.sub.max and the adjacent FFT sample k.sub.max+1. In one aspect of
the disclosure, a weighted average of the angle .theta..sub.1 and
angle .theta..sub.2 can provide a rough (coarse) spur frequency
estimate. This rough estimated spur frequency can then be used with
the cost function (8) to find a rough (coarse) value of the
duration N (rough estimated duration), which can be followed by a
fine frequency search and a fine search for the duration N. The
rough spur frequency estimate is less accurate than the fine spur
frequency estimate. Similarly, the rough duration N estimate is
less accurate than the fine duration N estimate.
[0046] FIG. 7 is a flow chart illustrating a spur parameters
determination method 700 in accordance with some aspects of the
disclosure. In one example, the method 700 may be performed using
the apparatus 100 or any suitable device. The method 700 may be
utilized to determine the five spur parameters A, F.sub.spur, N, a,
and .phi. of the above described equations. It is assumed that the
apparatus can receive a signal and perform an FFT on the signal
samples to obtain the corresponding frequency domain data.
[0047] At block 702, the rough frequency estimation block 128 may
be utilized to determine a rough estimated value (first estimated
frequency) of the spur frequency F.sub.spur as a weighted average
of a first angle (formed by the samples k.sub.max and k.sub.max-1)
and a second angle (formed by the samples k.sub.max and
k.sub.max+1) (e.g., angles .theta..sub.1 602 and .theta..sub.2 604
of FIG. 6) using equation (9) below, as an example.
F spur_rough = - 0.5 * ( 1 - .theta. 1 .theta. 2 + .theta. 1 ) + F
+ 0.5 * ( 1 - .theta. 2 .theta. 2 + .theta. 1 ) ( 9 )
##EQU00010##
[0048] In equation (9), F.sub.spur.sub._.sub.rough is the rough
(course) estimated value of F.sub.spur, and F is the frequency of
the sampled peak (e.g., peak 606 of FIG. 6). At block 704, the
rough spur duration estimation block 122 may be utilized to
determine a rough estimated value (first estimated duration) of N
based on the rough value of the spur frequency
F.sub.spur.sub._.sub.rough using, for example, the cost function
(8) with a search size N.sub.total and a step size N=20. Referring
to FIG. 9, at block 902, the frequency variable of the cost
function is set equal to the rough estimated value of F.sub.spur,
which is determined in block 702. At block 904, the rough estimated
duration of the spur is determined by minimizing the cost function
(i.e., determining a minimum value of the cost function). In an
illustrative example, FIG. 8 is a graph illustrating examples of
rough estimated values of N reaching a value of about 350 when the
cost function (3) reaches a minimum value. In the graph of FIG. 8,
the x-axis represents the rough value of N while the y-axis
represents the value of the cost function.
[0049] At block 706, using the rough estimated value of N, the fine
spur frequency estimation block 126 may be utilized to determine a
fine estimated value of F.sub.spur (second estimated frequency)
using, for example, the cost function (8) with a search size of 500
Hz and a step size F.sub.spur=10 Hz. Referring to FIG. 10, at block
1002, the duration variable of the cost function is set equal to
the rough estimated value of N that is determined at block 704.
Then, at block 1004, the fine estimated frequency of the spur is
determined by minimizing the cost function (i.e., determining a
minimum value of the cost function). At block 708, using the fine
estimated value of F.sub.spur, the fine spur duration estimation
block 124 may be utilized to determine the fine estimated value of
N (second estimated duration) using, for example, the cost function
(8) with a search size of 100 and a step size N=1. Referring to
FIG. 11, at block 1102, the frequency variable of the cost function
is set equal to the fine estimated value of F.sub.spur, which is
determined in block 706. At block 1104, the fine estimated duration
of the spur is determined by minimizing the cost function (i.e.,
determining a minimum value of the cost function).
[0050] At block 710, utilizing the fine estimated values of
F.sub.spur and N determined at blocks 706 and 708, the ASP
estimation block 130 may be utilized to determine the values of
parameters A, a, and .phi. using Equations (3), (4), and (6) as
follows.
A = R [ k max ] X [ k max ] ##EQU00011## .alpha. = 1 2 * ( mN .pi.
- N _ fine + 1 ) ##EQU00011.2## .PHI. = .theta. [ k max ] -
.pi..alpha. kmax * ( N _ - 1 + 2 .alpha. ) ##EQU00011.3## .alpha. k
max = F spur F S - k max N ##EQU00011.4##
[0051] Where: [0052] R[k] is the FFT of the received signal; [0053]
N is the estimated duration; [0054] F.sub.spur is the estimated
spur frequency; [0055] F.sub.s is the sampling frequency; [0056] N
is the FFT widow size; [0057] A is the estimated amplitude; [0058]
.phi. is the estimated initial phase offset; and [0059] a is the
estimated spur start location (e.g., a time offset from the start
of a measurement period or window).
[0060] While the method 700 has been described with exemplary
search sizes and step sizes for F.sub.spur and N, the method is not
limited to those values. In other aspects of the disclosure, the
search sizes and step sizes for F.sub.spur and N may have other
suitable values depending on for example the particular FFT
performed, sampling frequency, and spur frequency.
[0061] As those skilled in the art will readily appreciate, various
aspects described throughout this disclosure may be extended to any
telecommunication systems, network architectures and communication
standards. By way of example, various aspects may be extended to
other UMTS systems such as TD-SCDMA and TD-CDMA. Various aspects
may also be extended to systems employing Long Term Evolution (LTE)
(in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or
both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra
Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),
IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable
systems. The actual telecommunication standard, network
architecture, and/or communication standard employed will depend on
the specific application and the overall design constraints imposed
on the system.
[0062] Within the present disclosure, the word "exemplary" is used
to mean "serving as an example, instance, or illustration." Any
implementation or aspect described herein as "exemplary" is not
necessarily to be construed as preferred or advantageous over other
aspects of the disclosure. Likewise, the term "aspects" does not
require that all aspects of the disclosure include the discussed
feature, advantage or mode of operation. The term "coupled" is used
herein to refer to the direct or indirect coupling between two
objects. For example, if object A physically touches object B, and
object B touches object C, then objects A and C may still be
considered coupled to one another--even if they do not directly
physically touch each other. For instance, a first die may be
coupled to a second die in a package even though the first die is
never directly physically in contact with the second die. The terms
"circuit" and "circuitry" are used broadly, and intended to include
both hardware implementations of electrical devices and conductors
that, when connected and configured, enable the performance of the
functions described in the present disclosure, without limitation
as to the type of electronic circuits, as well as software
implementations of information and instructions that, when executed
by a processor, enable the performance of the functions described
in the present disclosure.
[0063] One or more of the components, steps, features and/or
functions illustrated in FIGS. 1-11 may be rearranged and/or
combined into a single component, step, feature or function or
embodied in several components, steps, or functions. Additional
elements, components, steps, and/or functions may also be added
without departing from novel features disclosed herein. The
apparatus, devices, and/or components illustrated in FIGS. 1-11 may
be configured to perform one or more of the methods, features, or
steps described herein. The novel algorithms described herein may
also be efficiently implemented in software and/or embedded in
hardware.
[0064] It is to be understood that the specific order or hierarchy
of steps in the methods disclosed is an illustration of exemplary
processes. Based upon design preferences, it is understood that the
specific order or hierarchy of steps in the methods may be
rearranged. The accompanying method claims present elements of the
various steps in a sample order, and are not meant to be limited to
the specific order or hierarchy presented unless specifically
recited therein.
[0065] The previous description is provided to enable any person
skilled in the art to practice the various aspects described
herein. Various modifications to these aspects will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other aspects. Thus, the claims
are not intended to be limited to the aspects shown herein, but are
to be accorded the full scope consistent with the language of the
claims, wherein reference to an element in the singular is not
intended to mean "one and only one" unless specifically so stated,
but rather "one or more." Unless specifically stated otherwise, the
term "some" refers to one or more. A phrase referring to "at least
one of" a list of items refers to any combination of those items,
including single members. As an example, "at least one of: a, b, or
c" is intended to cover: a; b; c; a and b; a and c; b and c; and a,
b and c. All structural and functional equivalents to the elements
of the various aspects described throughout this disclosure that
are known or later come to be known to those of ordinary skill in
the art are expressly incorporated herein by reference and are
intended to be encompassed by the claims. Moreover, nothing
disclosed herein is intended to be dedicated to the public
regardless of whether such disclosure is explicitly recited in the
claims. No claim element is to be construed under the provisions of
35 U.S.C. .sctn.112, sixth paragraph, unless the element is
expressly recited using the phrase "means for" or, in the case of a
method claim, the element is recited using the phrase "step
for."
* * * * *